I have a JD450C Crawler and I just replaced two hoses that control part of the 6 way blade. I was testing the dozer and all was fine for about 20 minutes then my hydraulics just quit. I used my backhoe to lift the blade so that I could walk it back home. The pump shaft is turning but wanted to know if any other diagnostic to try before removing the hydraulic pump. My quick assumption is the pump went out.
Pump shaft is turning, is the pump?... Did any air get into the system from the hose change? check your hyd tank filter/level.etc. Might be simple, might not.
Hydraulic tank is topped off as I added more after replacing the hoses. How can I actually tell if the pump is turning as I see that shaft rotating but the pump is located at the front of the engine.
I assume you checked the fluid level after hose replacement and running for a few minutes and it is up where it should be... is there any noise coming from the pump? I have seen pump shafts break or get stripped out and still appears like they are turning. Can't remember if the 450C pump has a shaft or is internal spline... edit: I see your post above so fluid is good
Yes, Fluid level is great. It seems to me there is a different noise coming from the pump but no blade movement at all from any lever position. I can see the shaft turning from the crank to the pump ....I believe it is spline shaft.
If it is a more 'rattly noise' then chances are the splines got buzzed off.
Does your 450 have a spring loaded pump disconnect coupling that allows you to disengage the hyd pump?... most or many did.. supposed to be a lever up near the front right side of the engine. I think its like a jaw coupling. My '75 450C does not have it. I wonder if somehow the coupling opened or broke.. or it could be shaft/spline/ etc... or maybe an open spool in the main valve body?. If you pull the grill you should be able to "feel" if the pump is turning I think.
Here is a pic of a 450B shaft and pump, I don't remember the C's having the same... but some early ones could... on the pump just two hoses and two bolts and it slide right out You can see the fork and slip collar for the pump disconnect, the lever is just inside the frame on the bottom of the pic.